Pancreatic Neuroendocrine Tumours: The Role of Endoscopic Ultrasound Biopsy in Diagnosis and Grading Based on the WHO 2017 Classification

One of the controversial issues in the diagnosis of pancreatic neuroendocrine tumours (pNETs) is the accurate prediction of their clinical behaviour. Objectives: The aim of the study was to evaluate the role of endoscopic ultrasound (EUS) biopsy in the diagnosis and grading of pNETs in a certified ENETS Center. Methods: A prospectively maintained database of EUS biopsy procedures was retrospectively reviewed to identify all consecutive patients referred to a certified ENETS Center with a suspicion of pNET between June 2014 and April 2017. The cytological and/or histological specimens were stained and the Ki-67 labeling index was evaluated. In patients undergoing surgery, the grade obtained with EUS-guided biopsy was compared with the final histological grade. The grade was evaluated according to the 2017 WHO classifications and grading. Results: The study population included 59 patients. EUS biopsy material reached an adequacy of 98.3% and was adequate for Ki-67 evaluation in 84.7% of cases. Twenty-nine patients (49.2%) underwent surgery. Of these, 25 patients had Ki-67 evaluated on EUS biopsy: the agreement between EUS biopsy grading and surgical specimen grading was 84%. Conclusion: EUS biopsy is an accurate method for the diagnosis and grading of pNETs based on the WHO 2017 Ki-67 labelling scheme.